BACKGROUND
1. Field of the Invention
[0001] The present invention relates to a method of compressing and decompressing In-phase/Quadrature
(I/Q) data between a digital unit (DU) and a radio unit (RU) in a Cloud Radio Access
Network (CRAN), and more particularly, to a method of compressing and decompressing
I/Q data between the DU and the RU in the CRAN that can significantly reduce an amount
of data transmitted and received between the DU and the RU in a way such that basic
units of compression are defined as bundles of basic frames defined in a Common Public
Radio Interface (CPRI) standard, and a header having information about an amount of
data remaining after compression for each of the basic units is defined so as to be
transmitted and received.
2. Discussion of Related Art
[0002] FIG. 1 is a block diagram showing a base station system having a general Cloud Radio
Access Network (CRAN) structure. As shown in FIG. 1, in a recent base station system,
the CRAN structure implemented by separating a digital signal processing unit (DU;
Digital unit) 10 and a radio signal processing unit (RU; Radio Unit) 20 of the base
station system has been widely introduced in order to reduce capital expenditure (CAPEX)
and operational expenditure (OPEX), and to ensure efficiency of equipment development.
Such a CRAN is one kind of Cloud Communication Center (CCC), and may reduce OPEX and
power consumption as well as significantly increase a wireless data capacity compared
to an existing system.
[0003] As described above, the DU 10 is concentrated in a DU center provided separately
in a station, whereas the RU 20 is provided in a service target area far away from
the DU 10. Accordingly, high-speed transmission and reception of baseband I/Q signals
between the DU 10 and the RU 20 is required, and therefore the DU 10 and the RU 20
are physically connected to an optical link or an Unshielded Twisted Pair (UTP). In
this instance, a plurality of frequency assignment (FA) and sector signals may be
mixed between the DU 10 and the RU 20, and therefore the number of optical cables
for connecting these signals may be determined in accordance with an I/Q data transfer
amount.
[0004] In this manner, since the DU 10 and the RU 20 are physically far apart from each
other, facility costs of the optical cable are significantly increased, and therefore
it is possible to reduce CAPEX by reducing the amount of data between the DU 10 and
the RU 20. A standard that is most commonly used in transmission and reception of
I/Q data between the DU 10 and the RU 20 is a Common Public Radio Interface (CPRI),
and a standard of the latest version (Ver 5.0) may support a line data rate of up
to 9.8304 Gbps.
[0005] Next, the RU 20 may include a frequency up-converting module, a frequency down-converting
module, a power amplifier, a filter, and the like. The DU 10 may include a data processing
unit for processing signals received from a terminal or signals transmitted to the
terminal, and the data processing unit may be connected with a network so that the
signals received from the terminal are transmitted to the network, and signals received
from the network are transmitted to the terminal.
[0006] Meanwhile, in order to reduce an amount of data between the DU 10 and the RU 20,
a method of reducing an amount of sampling through non-integral multiple re-sampling
using a separate interpolation/decimation scheme in each of the DU 10 and the RU 20
has been proposed. Since this method implements a larger size of Fast Fourier Transform/Inverse
Fast Fourier Transform (FFT/IFFT) compared to the number of subcarriers of data to
be transmitted in an Orthogonal Frequency Division Multiplexing (OFDM) system, an
amount of data may be reduced by reducing redundancy at frequencies through a low-pass
filter and interpolation/decimation. However, there is a fundamental limitation in
significantly reducing the amount of data transmitted and received between the DU
and the RU using only this method.
[0007] The paper
'R. Bandara: "A simple string compression Algorithm", internet article, July 10, 2011' suggests a simple compression method for SMS messages. For SMS messages the number
of allowed ASCII characters is restricted to 256 different characters. Normally ASCII
characters including all possible characters are represented by 8 bits, while the
256 characters allowed for SMS would occupy only 5 bits. Thus it is suggested to reduce
the SMS to 5 bit encoding such that in a given number of bits per SMS message more
information can be sent from the transmitter to the receiver.
SUMMARY OF THE INVENTION
[0008] The invention is defined in claims 1 and 6, respectively. Particular embodiments
are set out in the dependent claims.
[0009] The present invention is directed to a method of compressing and decompressing In-phase/Quadrature
(I/Q) data between a digital unit (DU) and a radio unit (RU) in a Cloud Radio Access
Network (CRAN), which can significantly reduce an amount of data transmitted and received
between the DU and the RU in a way such that basic units of compression are defined
as bundles of basic frames defined in a Common Public Radio Interface (CPRI) standard,
and a header having information about an amount of data remaining after compression
for each of the basic units is defined so as to be transmitted and received, thereby
reducing capital expenditure (CAPEX) and operational expenditure (OPEX) of a base
station.
[0010] According to an aspect of the present invention, there is provided a method of compressing
I/Q data transmitted and received between a DU and an RU in a CRAN structure, the
method including: (a) calculating a minimum value D
iMSB among meaningless higher-order bit digits

with respect to each of j-th I/Q samples having a predetermined resolution among
i-th unit blocks that are units of compression; and (b) transmitting each of the samples
after each of the samples is converted into a binary number and D
iMSB amount of higher-order bits, excluding a sign bit, are removed.
[0011] In the above-described configuration, a minimum compression rate is ensured in a
way such that a maximum value Q
iMSB among meaningful lower-order bit digits

with respect to each of the samples is further calculated in the (a) calculating,
a lower-order bit digit

to be removed is calculated by deducting D
iMSB from the minimum number of compressed bits B
MIN before the (b) transmitting. Preferably the (b) transmitting (b) is performed when

is 0 or smaller, whereas each of the samples is transmitted after

amount of lower-order bits are further removed when

is larger than 0.
[0012] In addition, the method further includes (c) additionally transmitting, in the form
of a header, code word information obtained by source-coding Q
iMSB or Q
iMSB so as to decompress a reception terminal.
[0013] In addition, a lossless coding method including Huffman coding may be applied for
the source-coding.
[0014] In addition, the (a) calculating to the (c) transmitting may be performed in units
of unit blocks, which are small sections obtained by segmenting a basic frame defined
in a Common Public Radio Interface (CPRI) standard.
[0015] In addition,

may correspond to the number of higher-order bits than a bit in which 1 initially
appears when the sample is a positive number, and may correspond to the number of
higher-order bits than a bit in which 0 initially appears after being converted into
a positive number when the sample is a negative number.
[0016] According to another aspect of the present invention, there is provided a method
of decompressing I/Q data between a DU and an RU in a CRAN, the I/Q data being compressed
according to the above method and received, between DU and RU in CRAN, the method
further including: (d) receiving binary bits of the sample and the header, and calculating
D
iMSB and

by

confirmed from the header; and (e) restoring to an original bit resolution of the
sample in a way such that the received binary bits are separated by

bits when

is 0 or smaller and D
iMSB number of 0 bits are inserted after a sign bit that is a first bit of the separated
binary bits, whereas the received binary bits are separated by

bits when

is larger than 0 and D
iMSB and

number of 0 bits are inserted after a first bit of a bit separated by

bits and a final bit.
BRIEF DESCRIPTION OF THE DRAWINGS
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0018] Exemplary embodiments of the present invention will be described in detail below
with reference to the accompanying drawings. While the present invention is shown
and described in connection with exemplary embodiments thereof, it will be apparent
to those skilled in the art that various modifications can be made.
[0019] Hereinafter, a method of compressing and decompressing In-phase/Quadrature (I/Q)
data between a digital unit (DU) and a radio unit (RU) in a Cloud Radio Access Network
(CRAN) according to an embodiment of the present invention will be described in detail
with reference to the accompanying drawings.
[0020] In the following Table 1, a variety of parameters used in the method of compressing
and decompressing IQ data between the DU and the RU in the CRAN are defined.
[Table 1]
Parameters |
Explanation |
dCompUnit |
Basic unit of compression |
That is, proposed algorithm is performed with respect to dCompUnit number of basic frames at a time (basic frame refers to 260.4 nsec as a time unit
defined in CPRI standard) |
Unit Block |
Small sections obtained by segmenting dCompUnit section |
Digital samples included in dCompUnit section are divided into several Unit blocks. Samples included in the same Unit block
are compressed so as to have the same Exponent after compression |
L |
Original bit resolution of digital sample |
M |
Total number of digital samples included in dCompUnit |
N |
The number of digital samples included in each Unit Block |
K |
The number of Unit blocks included in dCompUnit |
Bi |
i-th Unit Block (i= 1, 2, ..., K) |
Si.j |
j-th digital sample of i-th Unit Block (j= 1, 2, ..., N) |

|
Meaningless higher-order bit digit of j-th digital sample of i-th Unit Block, that is, refers to bits that do not affect corresponding sample value
Positive value -> the number of higher-order bits than bit in which 1 initially appears |
Negative value -> the number of higher-order bits than bit in which 0 initially appears
after being converted into positive number |

|
Meaningful lower-order bit digit of j-th digital sample of i-th Unit Block (corresponding to Exponent value)

|
DiMSB |
Minimum value among
 values of arbitrary i-th Unit Block

for a given i |
QiMSB |
Maximum value among
 values of arbitrary i-th Unit Block

for a given i |
BMIN |
Minimum number of compressed bits. The number of compressed bits per sample should
be BMIN or larger. This value is provided to compression terminal and restoration terminal
in advance, or is transmitted from compression terminal to restoration terminal only
once before transmitting data. |

|
Exponent value actually used when transmitting digital samples included in Bi. Exponents after compression of samples included in Bi are all the
 same as . |

|
Exponent values of digital samples included in Bi informing decompression terminal through header or the like.

may be specific code value corresponding to each of Exponent values for improving
compression efficiency. |
For example, transmitting result code value after performing Huffman coding with respect
to Exponents occur in dCompUnit |
PiLSB |
Subtracting the number of meaningless higher-order bits of i-th Unit Block from the minimum number of compressed bits. When this value is 0 or
smaller, compression sufficiently satisfying minimum compression bit is possible through
MSB removal, and when this value is 1 or larger, PiLSB number of LSBs are removed and compressed |
 |
[0021] FIG. 2 is a flowchart showing a method of compressing I/Q data between a DU and an
RU in a CRAN. As shown in FIG. 2, in the method of compressing I/Q data between the
DU and the RU in the CRAN, in step S10, the method may receive a digital I/Q sample
(hereinafter, simply referred to as "sample") in a unit of
dCompUnit, which is a basic unit of compression.
[0022] Next, in step S20, "
i" representing an order of unit blocks that are small sections obtained by segmenting
dCompUnit may be set as 1.
[0023] In step S30, a meaningless higher-order bit digit

in a j-th sample of the i-th unit block
Bi may be calculated. Here,

may denote bits that do not affect corresponding sample values even though the bits
are removed.

may correspond to the number of higher-order bits than a bit in which 1 initially
appears when the sample is a positive number, and may correspond to the number of
higher-order bits than a bit in which 0 initially appears after being converted into
a positive number when the sample is a negative number.
[0024] FIG. 3 is a diagram showing an example of

referring to bits that do not affect corresponding sample values even though the
bits are removed. In FIG. 3, an example in which an original bit resolution
L of the digital sample is 15, and a signed 2's complement is used. As shown in FIG.
3, when the sample is a positive number,

is 5, corresponding to the number of bits b
9 to b
13, which are higher-order bits than b
8, which is the bit in which 1 initially appears. When the sample is a negative number,

is 5, corresponding to the number of bits b
9 to b
13, which are higher-order bits than b
8, which is the bit in which 0 initially appears after conversion into a positive value.
[0025] Next, in step S40, a minimum value D
iMSB among

of the i-th unit block, and a maximum value Q
iMSB among

which is a meaningful lower-order bit digit (corresponding to an exponent value)
of the j-th sample of the i-th unit block, may be calculated. Here,

and Q
iMSB may be calculated by the following Equations 1 and 2:

[0026] Next, in step S50, a value

obtained by subtracting the number of the meaningless higher-order bits of the i-th
unit block from the minimum number of compressed bits may be calculated by the following
Equation 3:

[0027] In step S60, it may be determined whether

is 0 or smaller. Here, when

is 0 or smaller, the method may proceed to step S70. In step S70, samples included
in
Bi may be converted into a binary number, a higher-order D
iMSB bit excluding a sign bit may be removed, and then only a Q
iMSB bit may be transmitted. On the other hand, when

is larger than 0, the method may proceed to step S80. In step S80, the samples included
in
Bi may be converted into a binary number, a higher-order D
iMSB bit and a lower-order

bit excluding a sign bit may be removed, and then only a B
MIN bit may be transmitted.
[0028] Next, in step S90, a Q
iMSB value for the samples included in
Bi or a corresponding code may be transmitted through a header.
[0029] Next, in step Sd100,
i may be increased by 1 and then the method may return to step S30.
[0030] FIG. 4 is a flowchart showing a method of decompressing data compressed by the method
of FIG. 2. As shown in FIG. 4, in step S110,
i may be set as 1, and in step S120, binary bits of samples included in an i-th unit
block
Bi and corresponding header information Q
iMSB may be received.
[0031] Next, in step S130, D
iMSB may be calculated by the above Equation 2.
[0032] In step S140,

may be calculated by the above Equation 3.
[0033] In step S150, it may be determined whether

is 0 or smaller. Here, when

is 0 or smaller, the method may proceed to step S160. In step S160, an amount Q
iMSB of the received binary bits may be separated, and then D
iMSB number of 0 bits may be inserted after a first bit, e.g., a sign bit, of the separated
bits. On the other hand, when

is larger than 0, the method may proceed to step S170. In step S170, (

) number of the received binary bits may be separated, and then D
iMSB and

number of 0 bits may be respectively inserted after a first bit of the separated
bits, that is, a sign bit and a final bit.
[0034] In step S180, the samples included in
Bi may be restored to
L bits sample. Next, in step S190,
i may be increased by 1, and the method may then return to step S120.
[0035] The following Table 2 shows an example of setting parameters in a case in which M=16,
K=4, N=4, L=15, and B
MIN=6 are satisfied in the method of compressing and decompressing the I/Q data.

[0036] In the above Table 2, D
iMSB is calculated for each of 4 samples when N=4 is satisfied, and bits to be actually
compressed in units of N samples are determined compared to the minimum number of
compressed bits B
MIN, which is a design parameter. In this instance, when D
iMSB is larger than or equal to B
MIN (case I), the samples may be compressed according to a method of removing D
iMSB (excluding a sign bit) amount of higher-order bits starting from the Most significant
Bit (MSB) of the N sample, and the compressed samples may be transmitted. In this
process, the Q
iMSB value and a code (for example, Huffman code or the like) corresponding to the Q
iMSB value may be transmitted through a header, so that a reception terminal may perform
restoration (decompression).
[0037] On the other hand, when D
iMSB is smaller than B
MIN (case II in Table 2), a minimum compressed bit condition may be satisfied by additionally
removing P
iLSB number of bits from the Least significant Bit (LSB) as well as the MSB. In this case
(case II in Table 2), a partial loss of data bits may occur, but a compressed parameter
may be set to satisfy an Error Vector Magnitude (EVM) deterioration condition due
to compression, for example, to be 1% or less.
[0038] FIG. 5 is a diagram showing an example of a data compression and decompression process
in a case in which

is satisfied. An example of FIG. 5 in which D
iMSB is 7 and B
MIN is 6 may correspond to the case I of Table 2, and therefore a transmission terminal
may transmit data while removing from the data b
7 to
13, which are bits corresponding to D
iMSB, and compressing the data, and a reception terminal may decompress the compressed
data by inserting 0s into b
7 to
13.
[0039] FIG. 6 is a diagram showing an example of a data compression and decompression process
in a case in which

is satisfied.
[0040] An example of FIG. 6 in which D
iMSB is 5 and B
MIN is 6 may correspond to the case II of Table 2. Therefore, a transmission terminal
may compress data by removing from the data bits b
9 to b
13 corresponding to D
iMSB, and further removing from the data P
iLSB number of LSB side lower-order bits, e.g., b
0, and may then transmit the compressed data. In addition, a reception terminal may
decompress the compressed data by filling b
9 to b
13 and b
0 with 0s.
[0041] The I/Q data generated after performing the IFFT operation may be approximated as
Gaussian noise of multicarrier signals, and the approximated signals may have a large
Peak-to-Average Power Ratio (PAPR). A case in which a size of the signal subjected
to the IFFT operation is large corresponds to a case in which lower-order bits of
a sample do not have a relatively large meaning compared to the signal size, and a
case in which the size of the signal subjected to the IFFT operation is small corresponds
to a case in which higher-order bits of the sample are meaningless, because the higher-order
bits of the sample are filled with meaningless values.
[0042] Therefore, in the method of compressing and decompressing the I/Q data, by removing
lower-order bits when a value of an input sample is relatively large, and removing
higher-order bits when the value of the input sample is relatively small, the I/Q
data can be effectively compressed without any loss, and therefore a transmission
terminal and a reception terminal can compress and decompress data by transmitting
variable bit removal information in a separate header.
[0043] In addition, in the method of compressing and decompressing the I/Q data, a minimum
compression rate can be ensured, thereby stably performing mixing of data transmitted
through a CPRI or the like. The input sample can be basically compressed without any
loss, and lower-order bits (LSBs) can be additionally removed only in a case in which
a minimum compressed bit condition cannot be satisfied, thereby compressing data while
minimizing loss of data bits.
[0044] The header information may be shared in the transmission terminal and the reception
terminal through a separate lookup table, and separate encoding/decoding, for example,
a Huffman encoding/decoding algorithm may be applied in order to reduce an amount
of data of the header.
[0045] Meanwhile, delay for compression/decompression may differ in accordance with a size
of a compression unit, and may be determined as shown in the following Equation 4
based on trade-off between a compression rate and delay.

[0046] In the following Table 4, when L=15 and B
MIN =8 are set, a simulation test result of a data compression rate and EVM deterioration
due to compression by generating Long Term Evolution (LTE) 10 MHz 64Quadrature Amplitude
Modulation (QAM) signals is shown. The EVM deterioration is less than 0.02%, and compression
of about 40% or more may be possible.
[Table 3]
dCompUnit [Basic Frame] |
EVM deterioration [%] |
Compression rate [%] |
Delay [usec] |
Total |
Guaranteed |
1 |
0.0113 |
41.53 |
-5 |
0.260 |
2 |
0.0113 |
45.34 |
20.83 |
0.521 |
4 |
0.0113 |
47.55 |
33.75 |
1.042 |
8 |
0.0113 |
48.77 |
40.21 |
2.083 |
16 |
0.0113 |
49.39 |
43.44 |
4.167 |
32 |
0.0113 |
49.65 |
45.05 |
8.333 |
64 |
0.0113 |
49.8 |
45.86 |
16.667 |
128 |
0.0113 |
49.95 |
46.26 |
33.333 |
[0047] As described above, according to an embodiment of the present invention, the method
of compressing and decompressing the I/Q data between the DU and the RU in the CRAN
may significantly reduce an amount of data transmitted and received between the DU
and the RU in a way such that basic units of compression are defined as bundles of
basic frames defined in a Common Public Radio Interface (CPRI) standard, and compression
related header information is additionally transmitted and received, whereby a plurality
of sectors or carrier signals may be transmitted to the same optical cable. As a result,
it is possible to reduce capital expenditure (CAPEX) and operational expenditure (OPEX)
for networking between the DU and RU.
[0048] In addition, according to an embodiment of the present invention, since a stable
system operation is possible when a minimum compression rate is ensured in application
of compression based on the CPRI standard, the method of compressing and decompressing
the I/Q data between the DU and the RU in the CRAN may designate a momentary compression
rate which should be minimally attained by satisfying a limiting condition in which
a bit resolution of each of result samples obtained by performing compression cannot
exceed a maximum bit resolution set by a user.
[0049] In addition, an amount of a header may be reduced by applying a source coding scheme
to a header that is additionally generated for compression/restoration, and therefore
the method according to an embodiment of the present invention, which is an independent
concept from a conventional compression method by re-sampling, may be applied simultaneously
together with the existing method, thereby obtaining an additional compression effect
beyond that provided by the existing method.
1. Ein Verfahren zum Komprimieren von Inphase/Quadratur (I/Q)-Daten, die zwischen einer
digitalen Einheit (DU) und einer Funkeinheit (RU) in einer Cloud Radio Access Network
(CRAN)-Struktur übertragen und empfangen werden, wobei das Verfahren die folgenden
Schritte umfasst:
(a) Berechnen (S30) eines Wertes DiMSB, der der minimale Wert unter bedeutungslosen Bitziffern

höherer Ordnung in Bezug auf jeden der j-ten I/Q-Abtastwerte mit einer vorbestimmten
Auflösung unter i-ten Einheitsblöcken ist, die Komprimierungseinheiten sind, wobei
beim (a) Berechnungsschritt eine minimale Komprimierungsrate in einer solchen Weise
sichergestellt wird, dass ein Wert QiMSB der der maximale Wert unter bedeutungsvollen Bitziffern

niedrigerer Ordnung in Bezug auf jeden der Abtastwerte ist, weiter berechnet wird
(S40);
(b) Berechnen (S50) einer Bitziffer PiLSB niedrigerer Ordnung, die durch Abziehen von DiMSB von der minimalen Anzahl von komprimierten Bits BMIN vor der (c) Übertragung (S90) zu entfernen ist;
(c) Übertragen (S90) jedes der Abtastwerte, nachdem jeder der Abtastwerte in eine
Binärzahl umgewandelt wurde und DiMSB Anzahl der Bits höherer Ordnung, mit Ausnahme eines Vorzeichenbits, entfernt wurden;
und
(d) zusätzliches Übertragen, in Form eines Headers, von Codewort-Informationen, die
durch Quellencodierung QiMSB erhalten werden, um sie an einem Empfangsterminal zu dekomprimieren.
2. Das Verfahren nach Anspruch 1, wobei das (c) Übertragen (S90) ausgeführt wird, wenn
PiLSB 0 oder kleiner ist (S60), während jeder der Abtastwerte übertragen wird, nachdem
PiLSB Anzahl von Bits niedrigerer Ordnung (S80) weiter entfernt wurden, wenn PiLSB größer als 0 ist.
3. Das Verfahren nach Anspruch 1 oder 2, wobei für die Quellencodierung ein verlustfreies
Codierungsverfahren einschließlich Huffman-Codierung angewendet wird.
4. Das Verfahren nach den Ansprüchen 1, 2 oder 3, wobei das (a) Berechnen (S30) bis zum
(d) Übertragen in Einheiten von Einheitsblöcken durchgeführt wird, die kleine Abschnitte
sind, die durch Segmentierung eines Basisrahmens erhalten werden, der in einem CPRI-Standard
(Common Public Radio Interface) definiert ist.
5. Das Verfahren nach einem der Ansprüche 1 bis 4, wobei

der Anzahl von Bits höherer Ordnung entspricht, die einen anderen Wert als ein Bit,
in dem anfangs 1 erscheint, haben, wenn der Abtastwert eine positive Zahl ist, und
der Anzahl von Bits höherer Ordnung entspricht, die einen anderen Wert als ein Bit,
in dem anfangs 0 erscheint, haben, nachdem sie in eine positive Zahl umgewandelt wurden,
wenn der Abtastwert eine negative Zahl ist.
6. Ein Verfahren zum Dekomprimieren von I/Q-Daten zwischen einem DU und einem RU in einem
CRAN, wobei die I/Q-Daten gemäß dem Verfahren nach einem der Ansprüche 1 bis 5 komprimiert
und zwischen DU und RU in einem CRAN empfangen werden, wobei das Verfahren umfasst:
(e) Empfangen (S120) von binären Bits des Abtastwertes und des Headers, und Berechnen
von

die aus dem Header und Bits von DiMSB und PiLSB bestätigt werden; und
(f) Wiederherstellen (S180) einer ursprünglichen Bit-Auflösung des Abtastwertes in
einer solchen Weise, dass:
die empfangenen Binärbits durch

Bits getrennt (S160) werden, wenn PiLSB 0 oder kleiner ist, und DiMSB Anzahl von 0-Bits nach einem Vorzeichenbit, das ein erstes Bit der getrennten Binärbits
ist, eingefügt werden,
wohingegen die empfangenen Binärbits durch QiMSB-PiLSB Bits getrennt (S170) werden, wenn PiLSB größer als 0 ist und DiMSB und PiLSB Anzahl von 0 Bits nach einem ersten Bit eines Bits, der durch QiMSB-PiLSB getrennt wurde und einem letzten Bit eingefügt werden.
1. Procédé de compression de données en phase/quadrature (I/Q) qui sont émises et reçues
entre une unité numérique (DU) et une unité radio (RU) à l'intérieur d'une structure
de réseau d'accès radio en nuage (CRAN), le procédé comprenant les étapes qui suivent
:
(a) le calcul (S30) d'une valeur DiMSB qui est la valeur minimum parmi des chiffres de bit d'ordre plus élevé non empreints
de sens Di,jMSB en relation avec chacun de j-ièmes échantillons I/Q qui présentent une résolution
prédéterminée parmi des i-èmes blocs unitaires qui sont des unités de compression,
dans lequel, au niveau de l'étape (a) de calcul, un taux de compression minimum est
assuré d'une façon qui est telle qu'une valeur QiMSB qui est la valeur maximum parmi des chiffres de bit d'ordre plus faible empreints
de sens Qi,jMSB en relation avec chacun des échantillons est en outre calculée (S40) ;
(b) le calcul (S50) d'un nombre de chiffres de bit d'ordre plus faible PiLSB qui doivent être supprimés en déduisant le nombre DiMSB du nombre minimum de bits comprimés BMIN avant l'étape (c) d'émission (S90) ;
(c) l'émission (S90) de chacun des échantillons après que chacun des échantillons
est converti selon un nombre binaire et que le nombre DiMSB de bits d'ordre plus élevé, à l'exclusion d'un bit de signe, sont supprimés ; et
(d) l'émission de façon additionnelle, sous la forme d'un en-tête, d'une information
de mot de code qui est obtenue au moyen d'un codage source de la valeur QiMSB afin de réaliser une décompression au niveau d'un terminal de réception.
2. Procédé selon la revendication 1, dans lequel l'étape (c) d'émission (S90) est réalisée
lorsque le nombre PiLSB est égal ou inférieur à 0 (S60), tandis que chacun des échantillons est émis après
une suppression supplémentaire du nombre PiLSB de bits d'ordre plus faible (S80) lorsque le nombre PiLSB est supérieur à 0.
3. Procédé selon la revendication 1 ou 2, dans lequel un procédé de codage sans pertes
qui inclut un codage de Huffman est appliqué pour le codage source.
4. Procédé selon la revendication 1, 2 ou 3, dans lequel les étapes qui vont de l'étape
(a) de calcul (S30) jusqu'à l'étape (d) d'émission sont réalisées selon des unités
de blocs unitaires, qui sont de petites sections qui sont obtenues en segmentant une
trame de base qui est définie selon un standard d'interface radio publique commune
(CPRI).
5. Procédé selon l'une quelconque des revendications 1 à 4, dans lequel Di,jMSB correspond au nombre de bits d'ordre plus élevé qui présentent une valeur autre qu'un
bit au niveau duquel 1 apparaît initialement lorsque l'échantillon est un nombre positif,
et correspond au nombre de bits d'ordre plus élevé qui présentent une valeur autre
qu'un bit au niveau duquel 0 apparaît initialement après une conversion selon un nombre
positif lorsque l'échantillon est un nombre négatif.
6. Procédé de décompression de données I/Q entre une DU et une RU à l'intérieur d'un
CRAN, les données I/Q étant comprimées conformément au procédé selon l'une quelconque
des revendications 1 à 5 et étant reçues, entre la DU et la RU à l'intérieur du CRAN,
le procédé comprenant :
(e) la réception (S120) de bits binaires de l'échantillon et de l'en-tête, et le calcul
de bits Qi,jMSB, ce qui est confirmé à partir de l'en-tête, de bits de DiMSB et PiLSB ; et
(f) la restauration (S180) d'une résolution binaire originale de l'échantillon d'une
façon qui est telle que :
les bits binaires reçus sont séparés (S160) par des bits Qi,jMSB lorsque PiLSB est égal ou inférieur à 0, et que des bits de 0 selon un nombre DiMSB sont insérés après un bit de signe qui est un premier bit des bits binaires séparés,
tandis que
les bits binaires reçus sont séparés (S170) par QiMSB - PiLSB bits lorsque PiLSB est supérieur à 0 et que des bits de 0 selon un nombre DiMSB et PiLSB sont insérés après un premier bit parmi un bit qui est séparé par QiMSB - PiLSB bits et un bit final.